In the following Patent Document 1, a wireless power supply system in which a power-supplying device and a power-receiving device can be simplified is disclosed. Because the power-supplying device estimates a distance between a primary self-resonance coil of the power-supplying device and a secondary self-resonance coil of the power-receiving device and controls the supply of power according to the distance in this wireless power supply system, it is not necessary to estimate the above-described distance by performing communication with the power-receiving device. That is, because a communication function is unnecessary, the configuration of the power-supplying device and the power-receiving device can be simplified.